1. Field of the Invention
The present invention relates to an improved shift lever device for the automatic transmission of a vehicle and more particularly, to a shift lever device having a switch which functions both as a "P" or park position sensing switch and as a key interlock switch for eliminating the "P" or park switch, thus reducing wiring lines, reducing cost, and reducing the weight of the vehicle.
2. Description of Related Art
Various types of shift lever devices are known in the art. Generally, in a vehicle containing an automatic transmission, the shift range is accomplished by a reciprocating movement and the shift lever is provided with an indicating panel for indicating all of the shift ranges, disposed at one side thereof, so that the shift lever can be controlled by the driver's desire.
As shown in FIG. 1, a conventional shift lever device includes a shift lever 100 pivotally attached to a hinge axle 102 so as to rotate at a certain angle for shifting to a desired shift range position. The shift lever 100 is further provided with a detent plate 104 having a plurality of grooves 106, a detent pin 108 for selectively engaging one of the grooves 106 when the detent pin 108 moves along the detent plate by moving the shift lever 100. The shift lever 100 is moved by depressing a push button 120 disposed on knob 118. A shift lock release lever 102 is operated by a shift lock solenoid valve 110, a parking position switch 114 for sensing a "P" or park position of the shift lever 100, and a key interlock switch 116.
The conventional shift lever device operates as follows. After pushing the push button 120 when the shift lever 100 shifts to the "P" or park position, for parking, the parking position switch senses this step and transmits a signal to a transmission controlling unit (not shown). Thereafter, when the push button 120 is released, an ignition key (not shown) can be separated from a key hole (not shown) since the key interlock switch 116 is operated by the detent pin 108. At this time, even though the user pushes the push button 120 of the knob 118, a position change is impossible since the detent pin 108 is engaged in the groove 106 of the detent plate 104.
And at this time, when the user ignites through the ignition key and pushes a brake pedal (not shown), the transmission controlling unit transmits a signal to the shift lock solenoid valve 110 so that the shift solenoid valve 110 actuates. That is, the shift lock release lever 102 moves forward for releasing the locking of the detent pin 108. At this state, when the shift lever 100 shifts to another position, the parking position switch 114 transmits a signal to the transmission controlling unit for deactivating the shift lock solenoid valve 110, so that the shift lock release lever 102 returns to its original position.
Thus, for safety of driving, the ignition key can be removed from the key hole only when the shift lever 100 is in the "P" or park position, and only when the user operates the brake can the shift lever 100 be shifted to other positions. Therefore, the traffic accident can be eliminated and reduced.
However, since the conventional shift lever devices contain two switch systems, i.e. a parking position switch and a key interlock switch, the conventional shift lever devices are complicated in structure, expensive to manufacture, contain a plurality of distributing wires, and are heavy in weight.